Logic Script - calculating Accounts with BAS()

Hello experts,

I am trying to write a script that includes a BAS formula to gather the sum of all the descendants.  I want to pull the value of all, less a few accounts.  This is the line of code I have, and it gives me an error around the BAS formula.  Is there a better way to do this?

*WHEN ACCOUNT

*IS BAS(P_EA3700)

*REC(EXPRESSION = ([ACCOUNT].[BAS(P_EA3700)] - ([ACCOUNT].[A_51800020])), ACCOUNT = "A_FCST_3700", AUDITTRAIL = "CC")

When I put an actual Account in place of the BAS forumla, it works.  The EA3700 has a lot of accounts within it, and i need the value of all, less this 51800020 account, and a couple others I will add when I figure out this code.

Thanks!